FIG. 1 shows a configuration of a conventional inverter circuit (power supply circuit) capable of converting DC power into AC power by a step up/down operation.
As shown in the drawing, this inverter circuit is a combination of a step up/down chopper 100 and a single-phase inverter 110. The step up/down chopper 100 is a circuit which converts a DC voltage Edc into a voltage (hereinafter, referred to as Vdc) higher than a peak value of an AC voltage eac to be outputted and includes a DC reactor 101, switching elements 102 and 103, and smoothing capacitors 104 and 105. The single-phase inverter 110 is a circuit which converts a voltage Vdc into an AC voltage eac and includes switching elements 111 to 114, smoothing capacitors 105 and 117, and AC reactors 115 and 116.
According to the inverter circuit, DC power can be converted into AC power by a step up/down operation. Here, in order to constitute the inverter circuit, two circuits including the step up/down chopper 100 and the single-phase inverter 110 are necessary. Further, since the step up/down chopper 100 includes the DC reactor 101 which has a large volume and weight, and a high cost, the inverter circuit with the above-described configuration is consequently large and heavy.
For that reason, an inverter circuit (a power supply circuit: Patent Literature 1) which converts DC power into AC power with only a step up/down inverter without a DC reactor has been proposed. Here, the inverter circuit disclosed in Patent Literature 1 is configured to constitute a step down converter by switching a switch when an input DC voltage is larger than a peak value of an output AC voltage and to constitute a step up converter by switching the switch when the input DC voltage is smaller than the peak value of the output AC voltage. That is, a switching pattern and a control method need to be switched in accordance with input/output voltage conditions in the inverter circuit disclosed in Patent Literature 1. For that reason, a problem arises in that an AC waveform may be distorted around a switching voltage in the inverter circuit disclosed in Patent Literature 1.